Magnetic materials such as ferrites are widely used in passive and tunable electromagnetic signal processing, devices, such as phase shifters, circulators, isolators, filters, antenna substrates, and EMI suppression cores. Due to their excellent dielectric properties, they possess the advantages of low loss and high power handling capability relative to semiconductors. Usually, parameters of magnetic materials are controlled by an external magnetic field and/or permanent magnets thus allowing for tuning of device performances. Permanent magnets or current driven coils imply relatively large component size, weight, and cost, as well as slow response time in comparison to semiconductor based technologies.
Magnetoelectric (ME) materials are a practical solution in controlling the magnetic materials by tuning the electric field and/or voltage instead of external magnetic fields and would eliminate permanent magnets and tuning coils to overcome most of the disadvantages in the use of magnetic materials for devices such as ferrite microwave devices. This introduces the possibility of circuits where magnetic materials and semiconductors can be used on the same integrated chip. Furthermore, key advantages of magnetic materials, including low insertion loss and high power handling capability can be exploited without the penalty of added size, weight, and cost, as well as increased response time.
For these reasons, developing tools for analyzing ME materials has gained considerable importance. Although most often ME materials are operational at low temperatures, certain materials, such as hexaferrite of the Z-type (Sr—Z), are intrinsically magnetoelectric at room temperature, exhibiting strong magnetoelectric coupling coefficient. Previous reports on ME hexaferrite materials measured the DC properties of these materials upon the application of DC magnetic field. For example, the low frequency (˜1 kHz) dielectric constant has been measured as a function of DC magnetic field. Since these materials are ME, it is possible to measure the permeability of the material with the application of DC voltage (electric field). Measurement of permeability is critical for optimization of circuit design, especially in high-frequency application. However, permeability measurements require the use of a coaxial line setup, which has never before been used with applications of high DC voltage.